Stabilized polyoxyalkylene compositions



March 19, 1957 J. T. PATTON, JR 2,786,030

- STABILIZED PQLYOXYALKYLENE COMPOSITIONS Filed NOV. 25, 1953 FIGURE I 2 Sheets-Sheet, 1

PERCENT CARBONYL DEVELOPED IN POLYOXYALKYLENE COMPOUNDS AT IOOC.

3ond5 Polyoxyolkylene Compound of Exomplel 2. Polyoxyolkylene Compound of Example I O.|/ Phenothiozine 3. Polyoxypropylene Glycol l800 mm. 4. Polyoxypropylene Glycol I800 m.w. 0 Phenothiazine 5. Methyl Ether Polyoxypropylene Glyool 678 mm. 6. Methyl Ether Polyoxypropylene Glycol 678 m.w.+

O.l% Phenothiozine "i C O .D 5 o John T. Patton Jr.

IN VEN TOR.

Attorney March 19, 1957 J. T. PATTON, JR 2,786,080

smsmzsp POLYOXYALKYLENE COMPOSITIONS Filed Nov. 25, 1953 FIGURE 2 2 Sheets-Sheet 2 PERCENT CARBONYL DEVELOPED IN POLYOXYALKYLENE COMPOUNDS AT IOOC. 1

TI 20nd 3 l. Polyoxyolkylene Compound Example I 2. Polyoxyolkylene Compound Example l+ O.l%Diteriiury-Bu1y1-Meta-Cresol 3. Polyoxyulkylene Compound Example l+ O.|% Phenyl Beta -Nophthylumine 4. Polyoxyolkylene Compound Exomplel+ .3 OJ Phenothiuzine 2. C O .D E o .IO I

0 IO 20 30 4O 5O 6O 7O 80 TIME Days John T. Potion r- INVENTOR.

Attorney STABILIZED POLYOXYALKYLENE COMPOSITIONS John T. Patton, Jr., Wyandotte, Mich., assignor to Wyandotte Chemicals Corporation, Wyandotte, Mich., a corporation of Michigan Application November 25, 1953, Serial No. 394,319

13 Claims. (Cl. 260-6115) This invention relates to polyoxyalkylene compounds that are stabilized against oxidation and its deleterious efiects. More specifically, the present invention relates to polyoxyalkylene compounds having incorporated therein a small quantity of phenothiazine as 'a stabilizer.

Polyoxyalkylene compounds are a valuable and well known class of organic compounds that are used as synthetic lubricants, hydraulic fluids, detergents, plasticizers and in other diverse applications. A serious shortcoming of the polyoxyalkylene compounds is that they are highly susceptible to oxidation, particularly at elevated temperatures. Oxidation of these compounds produces strongly odoriferous products which are objectionable in many compositions, e. g. cosmetics. Such oxidation attack is particularly objectionable when the polyoxyalkylene compounds are employed as lubricants, since the resulting. oxidation products are highly corrosive in nature, and adversely change the viscosity characteristics of the lubricant. In some cases this tendency towards oxidation tats atent is so marked that high lubricant consumption is e'ncountered.

It has been previously suggested in the prior art that polyoxyalkylene compounds can be stabilized against oxidation by the incorporation therein of 0.5-5% of oxidation inhibitors, such as aromatic amines and phenolic compounds. While these prior art stabilizers are of some value, they are not sufliciently effective to satisfy the needs of the art. Stabilizers now in use are objectionable in that relatively large quantities (usually 1-2.5%) are required for efficient stabilization, and, on ageing, polyoxyalkylene compounds containing these stabilizers become highly colored.

It is an object of this invention to provide polyoxyalkylene compounds which are effectively stabilized against oxidation.

Another object of this invention is to provide stabilized polyoxyalkylene compounds amounts of a stabilizing compound.

Other objects and advantages ofthis invention will become apparent from the following detailed description thereof, when read in conjunction with the accompanying drawings, in which containing only minor Fig. 1 is a graph showing the rate of oxidation of polyoxyalkylene compounds containing stabilizers of the type defined herein, and

Fig. 2 is a graph showing the rate of oxidation of polyoxyalkylene compounds containing stabilizers of the type described herein as compared with the rate of oxidation of the same polyoxyalkylene compounds containing stabilizers of the type disclosed in the prior art.

It has been discovered that polyoxyalkylene compoundsare effectively stabilized against the-deleterious effects of oxidation by incorporating therein small quantities of phenothiazine, or carbocyclic alkyl-substituted'derivatives thereof.

The polyoxyalkylene compounds with which the present invention is concerned are characterized by having 2 recurring oxyalkylene groups of the following type in their structure:

R1 R1 ['i!-0l l. i.

wherein: R1, R2, R3 and R4 are hydrogen or hydrocarbon radicals. Of particular concern are those polyoxyalkylene compounds having molecular weights in excess of 250 and which may be utilized as hydraulic fluids, synthetic.

lubricants, detergents, etc.

The term polyoxyalkylene compound is used to designate those compounds which are obtained by condensing; a plural number of alkylene oxide molecules with aua organic compound containing one or a plurality of re-- Typical of such compounds are-.- polyoxyalkylene glycols, e. g. polyoxyethylene glycol,. polyoxypropylene glycol, the heteric or mixed oxyethyl ene-oxypropylene polyglycols of U. S. 2,425,845, etc., the; monoethers obtained by condensing an alkylene oxide: with a monohydric alcohol or phenol and the monoesters:

active hydrogen atoms.

obtained by condensing an alkylene oxide with a monobasic carboxylic acid. Another class of compounds included within the scope of the term are the conjugated sequential condensation products of propylene and ethylene oxide with reactive hydrogen compounds containing a single reactive hydrogen atom. These compounds have the following formula:

Y is the residue of an organic compound containing one reactive hydrogen compound,

n has an average value of at least 6.4, as determined by hydroxyl number, and

m has a value such that the oxyethylene groups constitute 25-90%, by weight, of the compound.

The polyoxypropylene polymer is the condensation; product of propylene oxide and an organic compound. containing a plurality of reactive hydrogen atoms and. has a molecular weight of at least 900, as determined;

by hydroxyl number,

n is an integer,

x is an integer not larger than the number of reactive hydrogen atoms present in the organic compound from which the polyoxypropylene polymer is derived, and

l n and x have values suchthat the oxyethylene content constitutes 20-90%, by weight, of the compound. The preparation and structure of the abovecompounds are described in detail in the copending application of Lester G. Lundsted, Serial No. 386,945, filed October 19,

1953 now U. S. 2,674,619 and that description is incorporated herein by references. A related and preferred class of compounds are those conforming to the above a formula in which the polyoxypropylene polymer is pre-' pared by condensing propylene oxide with an aliphatic diamine or polymer thereof, e. g. ethylene diamine. These 1 compounds are likewise disclosed in the copending'ap" Patented Mar. 19, 1957 avsaoeo Pligt'iz iflngofi Lenten. G;--Lundsted, just referred to, which those obtained with the unstabilized polyoxyalkylene compounds, are set forth in Table I, below and are-plotted in Fig. 1:

Table I Percent Carbonyl-After, days Sample P01 0 alkylene Compound of Example 13 .3? 0.013 0. 06 0. 43 I Polyoxyalkylene Compound of Example '1 +7 0;1 %1' hppqf fin vinn 0. 018 0. 015 0. 028- 0.03? 0. 040- 0. 069 PolyOXYDrOPYljeneQlyool 0. 015 0.082 b 0. 43 PolyoxypropyleneGlycol 021%13116110- e thin ine 7 0. 015= 1 0.015 0.017 0. 028' 0.032 0.052 M ethylEthQlt.Rolyoxupropylene Glycol- 0. 000 0.062 0. 43 Methyl Ether Polyoxypropylene Glycol +0;1% phen0thiazlne 0.000 0.000 0. 006 0.017 0.024 0.052

Percentcarbonyldeter ned from calibration curve usmgamyl acetate as source of carbon yigroup.

b Concentration aboyeQAS, which is upper limit of calibration curve;

principle and. practice of the present invention2 to. those ski I edin theant:

EXAMPLE 1 A conjugated polyox-ypropylene-polyoxyethylene compound was: prepared as follows; (1) a-polyoxypropylene glycol of 1800 molecular weight was prepared by condensing 1.2 propylene oxide with propylene glycol and (2) one parLoftheso-prepared polyoxypropylene glycol was condensedwith .four parts ofethylene oxide. Two samples .oftheconjugated polyoxypropylene-polyoxyethylenelcornpoundi were prepared and to one of these wfas' added 0.1% .phenothiazine. These samples were-then put in open beakers and placed in an air-circulating oven at 100 C. At the end of 2 and 7 daysaliquots of the two samples were withdrawn and analyzed. The unstabilized compound developed an unpleasant odor and exhibitedastrong infrared absorption band at 527.. microns,

Referring to Fig. 1,.it will be seen thatphenothiazine, has a remarkable stabilizing actionon each'of. the three, different polyoxyalkylenecompounds., It will'b'e, noted that each of theunstabilized compounds was. oxidized. to,,a greater extent-in two days than was the corresponding sta'l'ailized compound" after 79days.

EXAMPLE 3 amine ,.'and" 011% i 216 f ditertiaryvbutylemeta-cresol were.

incorporated .into the conjugated ,polyoxypropylene-poly- XY? samples.

were aged; at 100 C.. as, set. forth vin Example 2.

Data showing 'theflevelopmentl of; carbonyl content with time. are, set forth in 'lfable. lI below fand are plottedin;

thus indicating the presence of carbonyl groups. Incon- Fig, ,2,:.

Table II Percent Carbonyl After. days a Sample g Eiagpl HI.) 0. 022 g Q. 34 0 43.3: Polyoxyalkyleneofipound-of- Example+ PBN'A 0.022 0.037 0.041 0. 058 o. 207 1043-...-. Polyoxyalkylcne-Oompound{of, t r l Example+P. 'r. 7 0.022 0.037 10.040; 0.1150:

7 Percent carbonyl determimnljrom calibration, eur e using amy l acetate as source at carbonyl group.-

b Ditertiary butyl-m-cresol;' Ph y B'mDh hEhmino; Phenothiazine.

1 Concentration above 0.43, which is upper-limit of callbration curve.

trast to these results, the phenothiazine stabilizedsample was odor freejand did not have. anabsorption bandof 5.7 'microns. These data demonstrate that phenothiazine inhibits the oxidation of polyoxyalkylene compounds, and that the infrared absorption at 5.7 microns isaquantitative measurementof the degree of oxidation that has taken EXAMPLE, 2

Referring to Fig. 2, it will be-notedthat, aftenany; finite periodof time; 111

compound inhibited with either of the priorlant stabilizers. It will also be noted that after a period of abontzoeays both' of *the' I prior} art stabilizing comgq il ds lost .their efficie'ncy' and tliereafter the" polyoxyalkylehe compoundcunie'). as the uninhibited -EXAMPLEA i sa n y y m yl n -nol smi hx n mm was oxidized as rapidly (as measured ,byrtlie' slppe .offthe polymer, haviriglf a calculatedmolecular" weight. of 000 was; prepared'g by condensing; propylene de' -withfethyb oxypropylenelpolymer was: condensed with Gas-pane of ethylene oxide. 'Iwo samples of the above compound were-prep re .andito one1was,added-.O;05.%- plien'othiazine. Ihe samples weraplaced. in: open beakers', in an airehe .con1pound described in Example 1 The lyoxyalkylene compoundgcont" iilng. plieno'thiazine 'had un'dergone less oxidation than .thel'same.

ajraaoso s circulating oven at 100 C. and samples were periodically withdrawn for analysis by the method described in Example 2. The results are set forth in Table III below:

pending application, Serial No. 257,499 filed l lovefrilzaeri 21, 1951, now abandoned.

In the appended claims, the term cogenen'c mixture Table III Percent Carbonyl after, days I Sample Polyoxyalkylene Compound 0.18 0.28 0.3 Polyoxyalkylene Compound+0.05% phenothisuine 0.011 0.015 0.019 0.026 0.026 0.028 0.144 0. 29 0.30 V

Percent carbonyl determined from calibration curve using amyl acetate as source of carbonyl group. From an inspection of the above table it is apparent 15 is used. This is a term that has been coined to designate that the phenothiazine efiectively stabilized the polyoxyalkylene compound. In contrast to these results, typical prior art stabilizers such as ditertiarybutyl-mcre'sol have virtually no stabilizing action on this particular polyoxyalkylene compound.

The reasons for the stabilizing action of phenothiazine are unknown, however, the stabilizing mechanism appears to be radically difierent from that of conventional stabilizers. The majority of conventional stabilizers, and including those disclosed in the prior art, operate through a preferential oxidation mechanism, i. e. the stabilizer is more easily oxidized than the polyoxyalkylene compound and, when in the presence of oxidizing agents, is oxidized in preference to the polyoxyalkylene compound. In inhibiting the oxidation of polyoxyalkylene compounds such stabilizers are destroyed, and eventually, after all the stabilizer has been converted to its oxidized form, the polyoxyalkylene compound undergoes oxidation at the same rate as the unstabilized compound. This type of mechanism is clearly illustrated by the curves in Fig. 2 showing the compounds stabilized with ditertiary-butylmeta-cresol and phenyl-beta-naphthylamine in which the rate of oxidation increased to the level of the uninhibited composition after about days, when presumedly the stabilizers were converted to their oxidized or inactive form. From an inspection of Fig. 2, it is the logical conclusion that phenothiazine is not being oxidized under the test conditions and that the polyoxyalkylene compound in which it is incorporated will be stabilized against oxidation almost indefinitely.

While phenothiazine is highly efiicient in stabilizing polyoxyalkylene compounds as a class, it is particularly eflicacious in stabilizing polyoxyalkylene compounds having molecular weights in excess of 250 and containing oxypropylene groups or mixtures of oxypropylene and oxyethylene groups. Because of their viscosity-temperature relationships, such polyoxy-alkylene compounds are eminently well suited for use as synthetic lubricants and/or hydraulic fluids. Phenothiazine is compatible with other standard additives customarily incorporated in polyoxyalkylene lubricants and hydraulic fluids, such as corrosion inhibitors, viscosity index improvers, pour point depressants, extreme pressure additives. etc.

It has been discovered that the structural group:

is responsible for the remarkable stabilizing action of phenothiazine. Therefore, while the herein described specific examples show polyoxyalkylene compounds containing phenothiazine as the stabilizing agent, carbocyclic substituted alkyl phenothiazines may be used in lieu thereof. Thus l-methyl-phenothiazine, 2-isopropylphenothiazine, 1,9-diethylphenothiazine, 3 methyl 6 ethylphenothiazine, etc., may be used to stabilize polyoxyalkylene compounds.

This application is a continuation-impart of my coa series of closely related, touching homologues that are obtained by condensing a plurality of alkylene oxide units with a reactive hydrogen compound (see U. S. Patent 2,549,438, particularly the section beginning at column 12, line 40).

What is claimed is: g

1. A composition of matter comprising a polyoxyalkylene compound and a stabilizing quantity of a compound selected from the group consisting of phenothiazine and carbocyclic alkyl-substituted phenothiazines.

2. The composition of claim 1 wherein the polyoxyalkylene compound has a molecular weight of at least 250.

3. A composition of matter comprising a polyoxyalkylene compound and a stabilizing quantity of phenothia zine.

4. The composition of claim 3 wherein the polyoxyalkylene compound has a molecular weight of at least 250.

5. A composition of matter comprising a polyoxypropylene glycol having a molecular weight in excess of 250 and a stabilizing quantity of phenothiazine.

6. A composition of matter comprising an alkyl ether of a polyoxypropylene glycol having a molecular weight in excess of 250 and a stabilizing quantity of phenothiazine.

7. A composition of matter comprising a polyoxypropylene-polyoxyethylene compound having the formula:

where equals at least 15; and (C2H40)a:+z' equals 20-90% of the total weight of the compound and a stabilizing quantity of phenothiazine.

8. A composition of matter comprising a polyoxyalkylene compound having a molecular weight in excess of 250 and ODS-5.0% phenothiazine.

9. A composition of matter comprising a polyoxypropylene glycol having a molecular weight in excess of 25 0 and 0.055.0% phenothiazine.

10. A composition of matter comprising an alkyl ether of a polyoxypropylene glycol having a molecular weight in excess of 250 and 0.05-5.0% phenothiazine.

11. A composition of matter comprising a polyoxyethylene-polyoxypropylene compound having the type formula:

HO-(C2H4O )2:(C3H60) 11(C2H4O .r'--H where:

y equals at least 15 and (C2H40):r+m equals 20-90% of the total weight of the compound and ODS-5.0% phenothiazine.

12. A composition of matter comprising (1) a cogeneric mixture of conjugated polyoxypropylene-polyoxyethylene compounds containing in their structure oxypropylene groups, oxyethylene groups and an organic radical derived from an organic compound containing a plurality of reactive hydrogen atoms; the compounds being characterized in that all of the oxypropylene groups are pres- 

1. A COMPOSITION OF MATTER COMPRISING A POLYOXYLAKYLENE COMPOUND AND A STABILIZING QUANTITY OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF PHENOTHIAZINE AND CARBOCYCLIC ALKYL-SUBSTITUTED PHENOTHIAZINE. 